The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to a disk drive base of the HDA. The head disk assembly includes at least one disk (such as a magnetic disk), a spindle motor for rotating the disk, and a head stack assembly (HSA). The printed circuit board assembly includes a servo control system in the form of a disk controller for generating servo control signals. The head stack assembly includes at least one head, typically several, for reading and writing data from and to the disk. The head stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached heads are moved relative to tracks disposed upon the disk.
The head stack assembly includes an actuator assembly, at least one head gimbal assembly, and a flex circuit assembly. A conventional “rotary” or “swing-type” actuator assembly typically includes a rotary actuator having an actuator body. The actuator body has a bore and a pivot bearing cartridge engaged within the bore to facilitate rotational movement of the actuator assembly between limited positions about an axis of rotation. In this regard, the pivot bearing cartridge includes a pivot shaft that is attached to both the disk drive base and the cover. A coil support extends from one side of the actuator body. An actuator coil is supported by the coil support and is configured to interact with one or more permanent magnetic elements, typically a pair, to form a voice coil motor. One or more actuator arms extend from an opposite side of the actuator body. Each head gimbal assembly includes a head that typically includes a transducer for writing and reading data and that is distally attached to each of the actuator arms. Each transducer typically includes a writer and a read element. The transducer's writer can be of a longitudinal or perpendicular design, and the read element of the transducer may be inductive or magnetoresistive. Each magnetic disk includes opposing disk surfaces. Data may be recorded along data annular regions on a single disk surface or both. As such, the head stack assembly may be pivoted such that each head is disposed adjacent to the various data annular regions from adjacent to the outer diameter to the inner diameter of each disk.
As mentioned above the head stack assembly includes the pivot bearing cartridge with the pivot shaft. The pivot shaft is attached to both the disk drive base and the cover. A lower end of the pivot shaft may be press-fit or threadedly engaged with the disk drive base. An opposing upper end may be threaded to receive a screw through the cover.
Due to cost, weight and/or sizing considerations, it is desirable to form the cover to be as thin as possible. However, as the relative thickness of the cover is reduced, the cover may tend to flex or warp (statically and dynamically) locally about the attachment location to the pivot shaft. This is problematic as the pivot shaft is coupled to the actuator and ultimately the heads. The flexure or warping of the cover may result a misalignment of the pivot shaft that results in a degradation of the disk drive performance. As such, maintenance of the relative lateral stiffness of the pivot shaft is of concern. Accordingly, there is a need in the art for an improved disk drive configuration in comparison to the prior art.